Lin-Chao Sue, Chiou Ni-Ting, Schuster Gadi
Institute of Molecular Biology, Academia Sinica, Taipei, 11529, Taiwan.
J Biomed Sci. 2007 Jul;14(4):523-32. doi: 10.1007/s11373-007-9178-y. Epub 2007 May 19.
The structure and function of polynucleotide phosphorylase (PNPase) and the exosome, as well as their associated RNA-helicases proteins, are described in the light of recent studies. The picture raised is of an evolutionarily conserved RNA-degradation machine which exonucleolytically degrades RNA from 3' to 5'. In prokaryotes and in eukaryotic organelles, a trimeric complex of PNPase forms a circular doughnut-shaped structure, in which the phosphorolysis catalytic sites are buried inside the barrel-shaped complex, while the RNA binding domains create a pore where RNA enters, reminiscent of the protein degrading complex, the proteasome. In some archaea and in the eukaryotes, several different proteins form a similar circle-shaped complex, the exosome, that is responsible for 3' to 5' exonucleolytic degradation of RNA as part of the processing, quality control, and general RNA degradation process. Both PNPase in prokaryotes and the exosome in eukaryotes are found in association with protein complexes that notably include RNA helicase.
根据最近的研究，描述了多核苷酸磷酸化酶（PNPase）和外切体的结构与功能，以及它们相关的RNA解旋酶蛋白。呈现出的图景是一种进化上保守的RNA降解机器，它从3'到5'进行核酸外切降解RNA。在原核生物和真核细胞器中，PNPase的三聚体复合物形成一个圆形甜甜圈状结构，其中磷酸解催化位点埋在桶状复合物内部，而RNA结合结构域形成一个RNA进入的孔，这让人联想到蛋白质降解复合物蛋白酶体。在一些古细菌和真核生物中，几种不同的蛋白质形成类似的圆形复合物，即外切体，它作为加工、质量控制和一般RNA降解过程的一部分，负责RNA从3'到5'的核酸外切降解。原核生物中的PNPase和真核生物中的外切体都与明显包括RNA解旋酶的蛋白质复合物相关联。
